Fraction

Lossless floats that may be used in matching, ordering and hashing

• The main goal of Fraction is to keep precision that floats cannot do
• Fractions can be used for matching and comparisons and thus for hashing
• Base arithmetic implemented upon num crate (rational module)
• Fraction struct implementation uses two u64 numbers and arithmetic on stack
• BigFraction struct implementation uses two limitless BigUint numbers and arithmetic on heap

Examples

Simple arithmetic

use fraction::Fraction;

fn main () {
  let mut fr = Fraction::zero ();

  fr = fr + Fraction::from (2);   // 0 + 2   = 2
  fr = fr / Fraction::from (0.5); // 2 / 0.5 = 4

  assert_eq! (fr, Fraction::from (4));
  assert_eq! (4.0f64, fr.to_f64 ());
}

Using as keys for a HashMap

use std::collections::HashMap;
use fraction::Fraction;

fn main () {
  let f = Fraction::from (0.75);

  let mut map: HashMap<Fraction, ()> = HashMap::new ();

  map.insert (f, ());

  assert! (map.contains_key (&Fraction::new (3, 4)));   // 0.75 == 3/4
  assert! (map.contains_key (&Fraction::new (6, 8)));   // 0.75 == 6/8
  assert! (map.contains_key (&Fraction::new (12, 16))); // 0.75 == 12/16
  assert! (! map.contains_key (&Fraction::from (0.5))); // 0.75 != 1/2
}

Comparison

use fraction::Fraction;

fn main () {
  let f14 = Fraction::new (1, 4); // 1/4 == 0.25
  let f12 = Fraction::new (1, 2); // 1/2 == 0.50
  let f24 = Fraction::new (2, 4); // 2/4 == 0.50
  let f34 = Fraction::new (3, 4); // 3/4 == 0.75

  assert_eq! (f12, f24);                   // 1/2 == 2/4
  assert_eq! (f34, f12 + f14);             // 3/4 == 1/2 + 1/4
  assert_eq! (f14, Fraction::from (0.25)); // 1/4 == 0.25
}

Change Log

[0.2.0] - 2016-08-28

Added

• num crate is a dependency now
• GenericFraction<T> implemented upon num::Ratio<T>
• BigFraction implementation based on num::BigRational (using heap)
• num::traits::Bounded trait implemented
• fn min_positive_value implemented
• num::traits::ToPrimitive trait implemented
• num::traits::Signed trait implemented
• From<f64> trait implementation now relies on format! macro instead of f64::fract
• BigFraction struct using num::BigUint
• fn format_as_float for BigFraction has been implemented

Changed

• The codebase has been rewritten and the license has been changed from LGPL-3 to MIT/Apache2 dual
• no more convertions into INFINITY on arithmetic overflows
• fn to_f64 now returns Option<f64> instead of f64 (num::trait::ToPrimitive implementation)
• From trait implementation uses fmt::Display from now on

Removed

• fn unpack removed
• std::cmp::Ord implementation removed in regard to NaN values

[0.1.0] - 2016-01-24

Added

• Basic implementation